Switch between versions of blender
Assuming you are working with Windows...
With the Windows Explorer visit the directory of Blender 2.8.
Find the Blender.exe (or how it is called under Windows...I am Linux guy...;)
Select that file
Click with the right mouse button it and select "Create shortcut here".
Move the newly created shortcut onto your desktop.
Do the same for the other version of blender.
If you will get an filename conflict, rename Blender.exe to Blender279.exe / Blender280.exe beforhand.